chore: update devDependencies to latest

- eslint: ^7.7.0
- mocha: ^8.1.1

Signed-off-by: Miroslav Bajtoš <mbajtoss@gmail.com>

package.json

@@ -34,10 +34,10 @@
   "devDependencies": {
     "chai": "^4.2.0",
     "chai-as-promised": "^7.1.1",
-    "eslint": "^6.8.0",
+    "eslint": "^7.7.0",
     "eslint-config-loopback": "^13.1.0",
     "loopback-datasource-juggler": "^3.32.0",
-    "mocha": "^6.2.0"
+    "mocha": "^8.1.1"
   },
   "ci": {
     "downstreamIgnoreList": [